1. Field of the Invention
The present invention relates to aerodynamic control systems for aircraft, and particularly to a supplementary control surface structure for airplanes for augmenting the conventional aileron control surfaces used to control motion about the roll axis of the airplane.
2. Description of the Related Art
Powered fixed wing aircraft, i.e., airplanes, are conventionally provided with ailerons at the trailing edge of each wing (for monoplanes) or at least one set of wings (for biplanes and other airplanes having multiple planes of wings). The ailerons move opposite one another to increase lift on one wing while decreasing the lift on the opposite wing, thereby causing the airplane to rotate about its roll axis, i.e., the longitudinal axis of the airplane. The deflection of the ailerons results in changes in the bending loads on the wings, and the downward deflected aileron momentarily increases the aerodynamic lift and corresponding bending loads of that wing over and above that required for level flight.
For any given degree of aileron (or other control) deflection, the stresses imparted to the aircraft structure typically increase with increases in airspeed. This generally can be a squared function, e.g., twice a given airspeed can result in four times the force on the structure for any given control deflection, for example. It will be seen that at some airspeed for a given airplane, it is possible to overstress the airplane structure by applying a relatively excessive control deflection. For this reason, maneuvering speeds are typically calculated for all airplanes, with the maneuvering speed generally defined as a maximum airspeed at which a full control deflection can be applied without overstressing the aircraft structure. Maneuvering speeds not only apply to control deflections, but can also apply to the increased aerodynamic loads that can be imparted to the structure due to sharp-edged gusts in turbulence, for example.
While only a single maneuvering speed (such as for positive forces in pitch) can be developed for a light or relatively small airplane, considering the factors involved, any given airplane can actually have a number of different maneuvering speeds for positive and negative forces in pitch, rolling forces to the left and right, and left and right yawing forces, as well. In fact, these forces can be additive, with a rolling pitch-up resulting in momentary loads on one wing that can exceed its structural limitations, even though the airplane may be flying somewhat below its published maneuvering speed. As the wings of the airplane support substantially the entire weight of the aircraft and also provide sufficient strength to absorb momentary increases in bending loads during rolling maneuvers, it would be desirable to alleviate at least a portion of stresses imposed upon the airplane due to aileron deflection, as can be beneficial in reducing a likelihood of relatively excessive stresses on the wings of the airplane.
Thus, a supplementary control surface structure for airplanes addressing the aforementioned problems is desired.